JP7867775B2 - Electrochromic device, lens unit, imaging device, window material, and method for driving electrochromic element - Google Patents

Description

This invention relates to an electrochromic device, a lens unit, an imaging device, a window material, and a method for driving an electrochromic element.

EC elements, which utilize electrochromic (hereinafter sometimes abbreviated as "EC") materials whose optical absorption properties (absorption wavelength, absorbance) change through electrochemical oxidation-reduction reactions, are known. EC elements, which can achieve both high transmittance when decolorized and low transmittance when colored, are applied to display devices, variable reflectance mirrors, variable transmission windows, variable ND (Neutral Density) filters, and other applications.

One type of ND filter is the gradient filter, which features a gradient in the light transmittance within the filter. Examples of gradient filters used in cameras include apodization filters, which soften the outlines of blurred images, and half-ND filters, which partially reduce the amount of light. If the transmittance gradient of such gradient filters can be electronically controlled, the range of image expression can be greatly expanded.

An electronically variable aperture (EMA) is known as an optical filter configured to partially change the transmittance of a variable transmittance region of an electrochromic element. Patent Document 1 discloses a variable aperture in which wiring is arranged along a set of electrodes and their surrounding seal. This variable aperture utilizes the resistance of the electrodes to control a portion of the variable transmittance region of the electrochromic element into a continuous transmittance gradient. Specifically, by increasing the effective voltage of the electrodes through DC or pulse-width modulated voltage application (a typical driving method for ECA elements), the low transmittance region can be expanded (the high transmittance region can be narrowed).

Special Publication No. 2002-537582

However, when the low-transmittance region of a gradient filter is expanded using the driving method described in Patent Document 1, the maximum transmittance (at the center) also decreases simultaneously. This decrease in maximum transmittance reduces the amount of transmitted light in the central region where high transmittance is desired. Therefore, electrochromic elements like those described in Patent Document 1 have the problem of leading to a decrease in signal quality and thus a degradation of acquired image quality when applied to lenses or cameras.

The object of this invention is to provide an EC device that can reduce the influence on the maximum transmittance when controlling the light transmission region of an EC element.

According to one disclosure of this specification, an electrochromic element having a pair of electrodes, an electrochromic layer disposed between the pair of electrodes, and wiring connected to the pair of electrodes, and a drive circuit connected to the electrochromic element and supplying voltage to the pair of electrodes via the wiring, wherein the electrochromic element forms a transmittance gradient in a transmittance-changing portion where the electrochromic layer is disposed due to the resistance of the electrodes, and the transmittance-changing portion has a first region that forms a first light-transmitting state at a position within the electrodes of the transmittance-changing portion close to the wiring, and An electrochromic device is provided, comprising: a second region that forms a second light-transmitting state at a position within the electrode further from the wiring than the first region; and the drive circuit, when controlling the transmittance gradation, repeatedly supplies a first voltage to promote an electrochemical reaction that reduces the transmittance of the electrochromic layer and a second voltage to promote an electrochemical reaction that increases the transmittance of the electrochromic layer, in a time domain where the electrochemical reaction of the electrochromic layer in the electrode in the first region is progressing and the change in transmittance of the first region is not visible.

Another disclosure of this specification provides a method for driving an electrochromic element, the electrochromic element comprising a pair of electrodes, an electrochromic layer disposed between the pair of electrodes, and wiring connected to the pair of electrodes, wherein the electrochromic element forms a transmittance gradient in a transmittance-changing portion where the electrochromic layer is disposed, due to the resistance of the electrodes, the transmittance-changing portion comprises a first region that forms a first light-transmitting state at a position within the electrodes in the transmittance-changing portion close to the wiring, and a second region that forms a second light-transmitting state at a position within the electrodes further from the wiring than the first region, and the method for driving an electrochromic element is provided, characterized in that when supplying a voltage to the pair of electrodes via the wiring to control the transmittance gradient, a first voltage that promotes an electrochemical reaction that decreases the transmittance of the electrochromic layer and a second voltage that promotes an electrochemical reaction that increases the transmittance of the electrochromic layer are repeatedly supplied, in a time domain in the first region where the electrochemical reaction of the electrochromic layer in the electrodes is progressing and the transmittance change in the first region is not visible.

According to the present invention, it is possible to provide an EC device that can reduce the influence on the maximum transmittance when controlling the light transmission region of an EC element.

This is a cross-sectional view showing the schematic configuration of an EC device according to the first embodiment of the present invention. This is a plan view showing the schematic configuration of an EC element according to the first embodiment of the present invention. This is a plan view illustrating the arrangement of wiring that forms a concentric transparency gradient. This is an energy diagram illustrating the overview of the electrode reaction in an EC element according to the first embodiment of the present invention. This graph illustrates the general method for applying voltage to the drive circuit of an EC device according to the first embodiment of the present invention. This figure illustrates the distance-transmittance profiles from the center of the apodization filters in Example 1 and Comparative Example 1, along with the corresponding transmitted images. This figure illustrates the distance-transmittance profiles from the center of the apodization filters in Examples 2 and 3. This is a schematic diagram showing an example of the configuration of an imaging device according to a third embodiment of the present invention. This figure shows an example of the configuration of a window material according to the fourth embodiment of the present invention.

[First Embodiment]
The schematic configuration of an electrochromic device (EC device) according to the first embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is a cross-sectional view showing the schematic configuration of the EC device according to this embodiment. Figure 2 is a plan view showing the schematic configuration of an EC element according to this embodiment. Figure 3 is a plan view illustrating the arrangement of wiring that forms a concentric transmittance gradation.

As shown in Figure 1, the EC device 1000 according to this embodiment includes an electrochromic element (EC element) 1009 and a drive circuit 1010 connected to the EC element 1009. The EC element 1009 includes a pair of electrodes 1001, an electrochromic layer (EC layer) 1002 positioned between the pair of electrodes 1001, and wiring 1004 to which the drive circuit 1010 is connected. The drive circuit 1010 is electrically connected to the pair of electrodes 1001 via the wiring 1004 and is electrically connected to the EC element 1009. The EC element 1009 may also have a base material 1006 supporting the pair of electrodes 1001, or a partition wall 1005 dividing the EC layer 1002. Furthermore, the EC device 1000 may include a temperature sensor (not shown). In this case, it is preferable that the temperature sensor has the function of detecting the temperature of the EC element 1009.

As shown in Figure 2, the EC element 1009 according to this embodiment is an EC element that forms a transmittance gradient in the transmittance changing portion 2010 of the EC element 1009 due to the resistance of a pair of electrodes 1001. The transmittance changing portion 2010 is the portion of the EC element 1009 where the EC layer 1002 is located. The transmittance changing portion 2010 has a first region 2001 that forms a first light transmission state at a location within the electrode 1001 close to the wiring 1004, and a second region 2002 that forms a second light transmission state at a location within the electrode 1001 further from the wiring 1004 than the first region 2001.

Next, the EC device 1000 and its components according to this embodiment will be described in more detail.
(EC element 1009)
An electrochromic (EC) element is a device that can electrically change the amount of light absorbed through the electrochemical reaction of an electrochromic compound (EC compound). EC elements include transmissive EC elements that control the amount of transmitted light and reflective EC elements that control the amount of reflected light. While the EC element according to this embodiment can be applied to either transmissive or reflective forms, transmissive EC elements are primarily used for optical filter applications.

EC elements can be made from inorganic materials or organic materials. Organic materials include polymeric organic materials and low-molecular-weight organic materials. The EC element according to this embodiment can use any of these EC materials. Of these, EC elements using low-molecular-weight organic materials are particularly preferred from the viewpoint of light absorption contrast and maximum transmittance.

While there are no particular limitations on the control range of the light absorption rate of the EC element, it is desirable that it encompasses a range that satisfies the performance requirements of a partially variable transmittance filter.

For example, an ideal control range for light absorption is 0% to 100%, while a practical control range is 0.1% to 95%. Furthermore, it is preferable to achieve a stepless gradient in controlling light absorption within these ranges.

(Electrode 1001)
The pair of electrodes 1001 have the role of controlling the coloration and decolorization of the EC layer 1002 by the voltage applied to them. In the case of a transmissive EC element 1009, both electrodes 1001 are made of a transparent electrode material. In the case of a reflective EC element 1009, at least one of the pair of electrodes 1001 is made of a transparent electrode material. In this case, the electrode that is further back in the optical path of the pair of electrodes 1001 may be a light-reflective electrode (for example, a metal electrode). The EC element 1009 exhibits EC characteristics when a voltage is applied between the pair of electrodes 1001.

The pair of electrodes 1001 preferably possess transparency, conductivity, and stability during the redox reaction of EC compounds. Examples of such materials include transparent conductive oxide materials such as indium tin oxide (ITO) and fluorine-doped tin oxide. The pair of electrodes 1001 may also be constructed by reducing the resistance value by providing metal nanowires or thin metal films to these electrode materials, or by using a transparent conductive film made of other conductive materials such as carbon nanotubes.

When a pair of electrodes 1001 are placed on a substrate (e.g., substrate 1006), the substrate may be made of a light-transmitting material. Here, "light-transmitting" means transmitting light, and can be defined, for example, as having a light transmittance of 50% to 100% for a target wavelength of light. The target wavelength of light here is the wavelength of light targeted by the EC element 1009, and a typical example is the wavelength range of visible light. Specific examples of light wavelengths include 420 nm to 700 nm. Specifically, glass or polymer compounds may be used as the substrate, and a coating such as an anti-reflective film may be provided as needed.

In this embodiment, the EC element preferably has a higher resistance for electrode 1001 than for wiring 1004 in order to form a transmittance gradient by electrode resistance. The specific resistance value may vary depending on the size of the EC element 1009, the distance between the pair of electrodes 1001, the EC layer, the gradient to be formed, etc. For example, when the EC element 1009 is applied to a camera filter, the electrode 1001 preferably has a resistance of 5Ω/□ to 1000Ω/□, more preferably 10Ω/□ to 200Ω/□, and most preferably 20Ω/□ to 100Ω/□.

(EC layer 1002)
The EC layer 1002 contains a material that exhibits EC properties (EC material).
The EC material includes EC compounds, which are organic EC compounds or inorganic EC compounds. The EC layer 1002 may be a fixed-type EC layer in which the EC compound is immobilized on the electrode, or it may be a floating-type EC layer in which the EC compound dissolved in an electrolyte (electrolyte solution, electrolyte gel, etc.) can move through the electrolyte. In this embodiment, a floating-type EC layer is preferably used as the EC layer 1002.

Examples of materials used in fixed-type electrochemical (EC) layers include the following: In inorganic EC elements, inorganic EC compounds such as tungsten oxide and iridium oxide are immobilized on the electrodes to form the fixed-type EC layer. In organic EC elements, high-molecular-weight EC compounds such as polythiophene and polyaniline, and low-molecular-weight EC compounds such as pyridine salt derivatives, aromatic amine compounds, and heterocyclic compound derivatives are immobilized on the electrodes to form the fixed-type EC layer.

In this embodiment, organic low-molecular-weight EC compounds are preferably used as the EC compound for the floating EC layer. Specific examples of organic low-molecular-weight EC compounds include derivatives of pyridine salts, aromatic amine compounds, and derivatives of heterocyclic compounds. These may be used in a dissolved state in a solvent. The solvent used for the electrolyte layer, described later, can be used as the solvent.

The EC layer 1002 described above includes both a normally transparent EC layer and a normally attenuating EC layer. A normally transparent EC layer is an EC layer that is transparent when no voltage is applied from the drive circuit, and attenuates when the effective voltage is applied. A normally attenuating EC layer is an EC layer that is attenuated when no voltage is applied, and becomes transparent when the effective voltage is applied. In this embodiment, a normally transparent EC layer is preferably used as the EC layer 1002. By using a normally transparent EC layer, it becomes possible to make the portion far from the power supply point transparent when forming a transmittance gradient using electrode resistance. This configuration is suitable for applications in variable apertures and apodization filters. Hereafter, for the sake of brevity, unless otherwise specified, the descriptions of the transparent and attenuating states will assume a normally transparent EC layer as an example; however, in the case of a normally attenuating EC layer, the notation for transparent/attenuating will be reversed.

EC elements include unipolar EC elements where the electrochemical reaction proceeds on one side of a pair of electrodes, and complementary EC elements where the electrochemical reaction of redox substances proceeds on both electrodes. While either type can be used as the EC element 1009 in this embodiment, a complementary EC element is preferred as a floating, self-decolorizing EC element because it allows for a larger attenuation ratio between the filter's transmission state and attenuation state, and for reasons described later.

In a typical complementary EC element, the EC layer comprises at least one of an anodic EC compound that changes from a transparent state to a dimmed state through oxidation and a cathodeic EC compound that changes from a transparent state to a dimmed state through reduction. In a floating EC element where the EC compound can move through an electrolyte, etc., an effective voltage must be applied to the electrodes and current must be continuously flowed to maintain the dimmed state due to the following reactions (1) to (4).

(1) The anodic EC compound (A ⁺ ) in the dimmed state (oxidized state) reaches the cathode electrode and undergoes a reduction reaction to become the transmitted state (A) (A ⁺ + ^e- → A).
(2) The reaction in which the cathodic EC compound ( ^C⁻ ) in the dimmed state (reduced state) reaches the anode electrode and undergoes an oxidation reaction, becoming the transmitted state (C) ( ^C⁻ → C + ^e⁻ ).
(3) A reaction in which an anodic EC compound in a dimmed state (oxidized state) undergoes a reduction reaction with a cathodic redox substance (including the EC compound) in a reduced state, resulting in a transparent state (A ⁺ + C- ^→ A+C)
(4) A reaction in which a cathodic EC compound in a reduced state reacts with an anodic redox substance (including the EC compound) in an oxidized state, resulting in a transparent state ( ^C⁻ + A⁺ → C + A⁻ ⁾

These reactions (1) through (4) are called self-decolorization reactions, and the EC elements that produce them are called self-decolorization type EC elements. Because self-decolorization type EC elements require continuous current flow, they easily generate a voltage drop due to electrode resistance based on Ohm's law, and thus easily create an effective voltage difference within the electrode surface. This makes it easy to form a transmittance gradient within the electrode of the transmittance change section. Therefore, complementary, floating, and self-decolorization type EC elements are preferably used as the EC element 1009 in this embodiment.

Among organic low-molecular-weight EC compounds that can be used in complementary EC elements, aromatic amine compounds, particularly dihydrophenazine derivatives, are preferred as anodic EC compounds due to their excellent durability. Furthermore, pyridine salt derivatives, especially viologen derivatives, are preferred as cathode EC compounds due to their excellent durability and light absorption ability in the attenuated state. In particular, the combination of dihydrophenazine derivatives and viologen derivatives is especially preferred because it can cover a wide visible light absorption region and operates at a low drive voltage.

The EC element 1009 may have an electrolyte layer containing an electrolyte. This electrolyte layer may be arranged integrally with the EC layer 1002, or it may be arranged overlapping the EC layer 1002. Preferably, the electrolyte layer is prepared by dissolving the electrolyte in a solvent. The solvent is selected according to the application, considering the solubility of the solute (including the EC compound), vapor pressure, viscosity, potential window, etc., but a polar solvent is preferred. Specifically, examples of solvents for the electrolyte layer include organic polar solvents such as methanol, ethanol, propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, acetonitrile, propionnitrile, benzonitrile, dimethylacetamide, methylpyrrolidinone, dioxolane, and water. Among these, cyclic ester compounds are preferred from the viewpoint of boiling point and solubility.

Furthermore, the EC layer 1002 may contain, as needed, an electrolyte, viscosity modifier, UV stabilizer, etc. The electrolyte can be incorporated into the EC layer in the form of the electrolytic layer described above.

A partition wall 1005 is preferably used to hold the EC layer 1002 and the electrolyte layer between the pair of electrodes 1001, and to maintain the distance between the two electrodes 1001. A sealing material is preferably used as the partition wall 1005. The sealing material is preferably chemically stable, impermeable to gases and liquids, and does not inhibit the oxidation-reduction reaction of the EC compound. Examples of sealing materials include inorganic materials such as glass frit, organic materials such as epoxy or acrylic resins, and metals.

The sealing material may also function as a spacer to define and maintain the distance between the pair of electrodes 1001. In this case, the sealing material may contain spacer material. If the sealing material does not have the function of defining the distance between the pair of electrodes 1001, a separate spacer may be placed to maintain the distance between the two electrodes 1001. Examples of spacer materials include inorganic materials such as silica beads and glass fibers, and organic materials such as polyimide, polytetrafluoroethylene, polydivinylbenzene, fluororubber, and epoxy resin. It is possible to define and maintain the distance between the electrodes 1001 using such spacers.

(Wiring 1004)
The EC element 1009 according to this embodiment has wiring 1004 for efficiently applying a drive voltage to a pair of electrodes 1001 from an external circuit such as a drive circuit 1010. The material used for the wiring is not particularly limited as long as it is a material with high conductivity per unit volume, but metallic materials, especially silver, copper, and aluminum, are preferred. The method for forming the wiring 1004 can be selected according to the characteristics of the wiring 1004, electrodes 1001, and substrate 1006, and for example, methods such as printing using metal paste, sputtering, and plating can be applied. By combining these formation methods with methods such as patterning and polishing, wiring 1004 of a desired shape can be formed in a desired area. The resistance of the wiring 1004 is preferably lower than the resistance of the electrodes 1001, and more preferably at least one order of magnitude lower than the resistance of the electrodes 1001.

The shape and arrangement of the wiring 1004 largely determine the pattern of the transmittance gradation of the EC element 1009. For example, when forming a concentric transmittance gradation such as in a variable aperture or apodization filter, a suitable arrangement of wiring 1004 is shown in Figure 3, where the wiring surrounds the outer circumference of the circular partition wall 1005 along the periphery of the circular electrode 1001. Furthermore, when forming a linear transmittance gradation such as in a half-ND filter, a suitable arrangement of wiring 1004 is shown in Figure 2, where the wiring is positioned along one side of the rectangular electrode 1001.

(Transparency gradient)
The EC device 1000 according to this embodiment forms a transmittance gradient in the transmittance changing section 2010 of the EC element 1009. The EC element 1009 is an element whose transmittance changes depending on the effective voltage of the electrode 1001. The transmittance gradient of the EC element 1009 is formed when a voltage drop occurs due to the electrode resistance of the electrode 1001 when current flows through the electrode 1001, thereby forming an effective voltage gradient within the electrode 1001.

As described above, the transmittance gradation is formed by the resistance of electrode 1001, and therefore different light transmission states are formed depending on the distance from wiring 1004, which has lower resistance than electrode 1001. Here, the light transmission state formed at a position within electrode 1001 of the transmittance change section 2010 close to wiring 1004 is called the first light transmission state, and the region where this first light transmission state is formed is called the first region 2001. Furthermore, the light transmission state formed at a position within electrode 1001 further from wiring 1004 than the first region 2001 is called the second light transmission state, and the region where this second light transmission state is formed is called the second region 2002. For a normally transparent EC element, the first light transmission state is a low light transmission state, and the second light transmission state is a high light transmission state. Conversely, for a normally dimming EC element, the first light transmission state is a high light transmission state, and the second light transmission state is a low light transmission state. Below, the light transmittance during transmittance gradation formation will be described using a normally transparent EC element as an example.

When the electrode 1001 of the transmittance changing section 2010 is viewed from a direction perpendicular to the electrode surface (e.g., top view in Figure 2), the region occupying 10% of the area ratio from the side with the lowest transmittance on the electrode surface is defined as the first region 2001. The region occupying 10% of the area ratio from the side with the highest transmittance on the electrode surface is defined as the second region. In this embodiment, a normally transparent EC layer is preferably used, which allows the portion far from the power supply to be in a transparent state. The normally transparent EC layer has the opposite high and low transmittance compared to a normally attenuating EC layer, making it suitable for applications in variable apertures and apodization filters. Furthermore, the normally transparent EC layer is often more advantageous than the normally attenuating EC layer from the viewpoint of maximum transmittance. Therefore, it is preferable that the first light transmission state has a lower light transmittance than the second light transmission state. Additionally, the gradient EC element that forms the transmittance gradient utilizes the difference in light transmittance within the element to achieve its effect. Therefore, when forming the transmittance gradient of the EC element 1009, it is preferable that there be a sufficient difference between the light transmittance of the first light transmission state and the light transmittance of the second light transmission state.

As an example of a specific value for the difference in light transmittance between the first and second light transmittance states when forming a transmittance gradient, it is preferable that the difference between the highest and lowest values be at least twice, more preferably at least four times, and most preferably at least eight times.

(Drive circuit 1010)
The drive circuit 1010 connected to the electrode 1001 of the EC element 1009 of the EC device 1000 according to this embodiment via wiring 1004 will be described using a normally transparent EC element as an example. The drive circuit 1010 drives the EC element 1009 by supplying voltage to the electrode 1001 via wiring 1004. The transmittance of the EC element 1009 decreases as the effective voltage of the electrode 1001 increases. The transmittance gradient formed in the transmittance changing section 2010 of the EC element 1009 of the EC device 1000 according to this embodiment is formed according to the effective voltage of the electrode, as a gradient of effective voltage is formed within the electrode 1001. The gradient of effective voltage within the electrode 1001 is formed by the voltage drop caused by the electrode resistance when current flows through the electrode 1001.

When controlling the transmittance gradient of an EC element using typical driving methods such as DC or pulse-width modulated voltage application (drive voltage/open-circuit voltage), control is achieved by changing the effective voltage of the electrodes. For example, increasing the applied voltage or the duty cycle of the drive voltage increases the effective voltage, thereby expanding the low transmittance region (narrowing the high transmittance region). However, when expanding the low transmittance region of a gradient filter using these driving methods, increasing the effective voltage applied to the EC element simultaneously reduces the maximum transmittance of the EC element. This decrease in maximum transmittance reduces the amount of light transmitted through the filter, and when applied to lenses or cameras, this leads to a decrease in signal strength and a reduction in image quality.

To solve this problem, the drive circuit 1010 according to this embodiment repeatedly supplies different voltages to the electrode 1001. That is, when controlling the transmittance gradation, the drive circuit 1010 of this embodiment repeatedly supplies a voltage that promotes an electrochemical reaction that reduces the transmittance of the EC layer 1002, and a voltage that promotes an electrochemical reaction that increases the transmittance of the EC layer 1002. The details of the voltage supply by this drive circuit 1010 will be explained using Figure 4 as an example, with a complementary EC element using an anodic EC compound (A) that becomes a low-light-transmitting state through oxidation and a cathodeic EC compound (C) that becomes a low-light-transmitting state through reduction. Figure 4 is an energy diagram of the electrode reaction of the EC element.

Figure 4(a) shows the electrode reaction of an EC element when a voltage (V _Fwd ) is applied to promote an electrochemical reaction that reduces the transmittance of the EC layer. Here, for example, we will explain the case where a voltage equal to the difference between the formula potential (E ^0' _A ) of the anodic EC compound and the formula potential (E ^0' _C ) of the cathodeic EC compound is applied. At electrode E1, the anodic EC compound undergoes an oxidation reaction and changes into an oxidized state, which is a low light-transmitting state. On the other hand, at electrode E2, the cathodeic EC compound undergoes a reduction reaction and changes into a reduced state, which is a low light-transmitting state. (In viologen derivatives, which are typical cathodeic EC compounds, the high light-transmitting state is a dication and the low light-transmitting state is a monocation, but here, the former is described as C and the latter as ^C- .) Then, a current (i _Fwd ) flows through the external circuit.

Figure 4(b) shows the case where a voltage (V _Fwd ) that promotes an electrochemical reaction to increase the transmittance of the EC layer is applied, following the voltage (V _Rev ) which is the opposite polarity of V _Fwd . Near electrode E1, there are many oxidized forms (low light transmittance state) of the anodic EC compound generated by the application of V _Fwd , and the application of V _Rev rapidly reduces these to a high light transmittance state. Similarly, near electrode E2, there are many oxidized forms (low light transmittance state) of the cathodeic EC compound generated by the application of V _Fwd , and the application of V _Rev rapidly oxidizes these to a high light transmittance state. Then, a current (i _Rev ) flows through the external circuit.

As described above, the drive circuit 1010 in this embodiment repeatedly supplies to the electrode 1001 a voltage that promotes an electrochemical reaction that reduces the transmittance of the EC layer 1002 and a voltage that promotes an electrochemical reaction that increases the transmittance of the EC layer 1002. This allows the drive circuit 1010 to increase the current that does not contribute to the reduction in the transmittance of the EC layer 1002. This current, which does not contribute to the reduction in the transmittance of the EC layer 1002, allows for the control of the voltage drop caused by the electrode resistance when current flows, without changing the transmittance of the EC layer 1002. This makes it possible to control the transmittance gradient in the transmittance changing section 2010 by controlling the effective voltage gradient within the electrode 1001.

A preferred voltage for reducing the transmittance of the EC layer 1002 is, although it varies depending on the size and resistance of the electrode 1001, at or above the absolute difference between the formula potential of the anodic EC compound and the formula potential of the cathode EC compound, minus 0.2 V. A more preferred example is a voltage at or above the absolute difference between the formula potential of the anodic EC compound and the formula potential of the cathode EC compound. This upper limit of voltage is determined by the voltage at which the EC layer 1002 can stably undergo repeated transmittance changes. The formula potential of the EC compound used in the EC layer 1002 can be estimated from the midpoint potential of the peak potentials of the oxidation and reduction waves obtained by cyclic voltammetry using a reference electrode in an electrolyte solution containing a single EC compound.

On the other hand, an example of a voltage that drives the electrochemical reaction to increase the transmittance of the EC layer 1002 is a voltage of 0V or less, where the voltage that decreases the transmittance of the EC layer 1002 is a positive voltage. A particularly preferred range for this voltage is a voltage with the opposite polarity (negative voltage) to the voltage that drives the electrochemical reaction to decrease the transmittance of the EC layer 1002. This is because applying a reverse voltage to the voltage that drives the electrochemical reaction to decrease the transmittance of the EC layer 1002 allows the electrochemical reaction to decrease the transmittance of the EC layer 1002 to proceed faster within a limited time domain than a short circuit (applying 0V). The lower limit of this voltage is determined by the voltage at which the EC layer 1002 can stably repeat the transmittance change. A typical example of this voltage is a voltage with the same absolute value but with the sign reversed, that drives the electrochemical reaction to decrease the transmittance of the EC layer 1002.

The drive circuit 1010 according to this embodiment repeatedly supplies a voltage that promotes an electrochemical reaction that reduces the transmittance of the EC layer 1002 and a voltage that promotes an electrochemical reaction that increases the transmittance of the EC layer 1002 when controlling the transmittance gradation. The drive circuit 1010 repeatedly supplies these voltages in a time domain in the first region 2001 where the electrochemical reaction of the EC layer 1002 at the electrode 1001 proceeds, and the change in transmittance in the first region 2001 is not substantially visible. Here, the phrase "in the first region" means the following: that is, in the first region 2001 which forms a first light transmission state at a position relatively close to the wiring 1004 in the electrode 1001 within the EC element 1009, the electrochemical reaction of the EC layer 1002 proceeds, and the change in transmittance is not substantially visible. This aims to verify the visual observation of the progress of electrochemical reactions and changes in transmittance in the first region 2001, which is relatively close to wiring 1004 and where electrochemical reactions occur relatively actively.

The requirements for the electrochemical reaction of the EC layer 1002 at electrode 1001 can be explained as follows. Consider the time domain (frequency) in which a voltage that promotes an electrochemical reaction that reduces the transmittance of the EC layer 1002 and a voltage that promotes an electrochemical reaction that increases the transmittance of the EC layer 1002 are repeatedly supplied. As this frequency is increased, the contribution of the electrochemical reaction of the EC compound through which a Faraday current flows decreases as a process at electrode 1001 of the EC layer 1002, and the charge-discharge process through which a capacitor current flows becomes dominant. If the frequency of this repeated voltage supply is applied in a relatively short time domain in which the charge-discharge process is dominant, a sufficient effective voltage is not applied to the charge transfer resistance corresponding to the electrochemical reaction involved in the increase or decrease in the transmittance of the EC layer 1002, and the EC layer 1002 does not become a low light transmittance state. This state is undesirable because it forms a transmittance gradient in the transmittance change portion 2010 of the EC element 1009. Therefore, a repeated voltage supply is performed at a frequency where the electrochemical reaction of the EC compound, which carries a Faraday current and promotes the electrochemical reaction of the EC layer 1002, is the primary reaction. The suitable frequency range for this repeated supply to promote the electrochemical reaction varies depending on the type and configuration of the EC element 1009. For example, with complementary and self-decolorizing organic low-molecular-weight EC elements, a frequency range of 10 kHz or less is preferred, 1 kHz or less is more preferred, and 300 Hz or less is most preferred.

The requirement that the change in transmittance be performed in a time domain where it is substantially invisible has two meanings, as follows: (1) As the frequency of repeated voltage supply is lowered, and the frequency becomes lower than the electrode reaction response of the EC compound, the electrochemical reaction of the EC compound, which produces a Faraday current, proceeds at the electrode 1001 of the EC element 1009, causing an increase or decrease in the transmittance of the EC layer 1002. If this increase or decrease in transmittance is visible, it will result in flickering of light passing through the EC element 1009, degrading the quality of the EC device 1000. The frequency range suitable for this substantially invisible condition varies depending on the application of the EC device 1000, particularly the detection speed of the light detector through the EC element 1009. Using the human eye as an example, the frequency of repeated voltage supply is preferably 24 Hz or higher, next preferably 30 Hz or higher, and even more preferably 60 Hz or higher, from the viewpoint of preventing the increase or decrease in transmittance from being visible. It is preferable to select the frequency to be used in relation to this value and the preferred frequency of the electrochemical reaction described above. Typical frequency examples are between 60 Hz and 300 Hz. (2) The driving circuit 1010 according to this embodiment primarily aims to control the steady-state gradation pattern of the EC element 1009 during driving. Therefore, a voltage that promotes an electrochemical reaction that reduces the transmittance of the EC layer 1002 and a voltage that promotes an electrochemical reaction that increases the transmittance of the EC layer 1002 are repeatedly applied in a time domain where the change in the transmittance of the EC element 1009 is substantially invisible. Furthermore, a suitable transmittance fluctuation range for this substantially invisible change is preferably 5% or less, and more preferably 1% or less.

A specific example of the drive circuit 1010 according to this embodiment will be described below with reference to Figure 5. The drive circuit 1010 can preferably vary the ratio of the time spent supplying the voltage that drives the electrochemical reaction to increase the transmittance of the EC layer 1002 and the voltage that drives the electrochemical reaction to decrease the transmittance of the EC layer 1002.

Figure 5 is a schematic diagram illustrating the voltage application method of the drive circuit 1010 according to this embodiment. In Figure 5, the vertical axis represents the voltage applied from the drive circuit 1010 to the EC element 1009, and the horizontal axis represents time. As shown in Figure 5, the drive circuit 1010 repeatedly applies a voltage (V _Fwd ) to the EC element 1009 that promotes an electrochemical reaction that reduces the transmittance of the EC layer 1002, and a voltage (V _Rev ) that promotes an electrochemical reaction that increases the transmittance of the EC layer 1002. The drive circuit 1010 performs this repeated voltage application in a time domain, period (T), in which the electrochemical reaction of the EC layer 1002 at the electrode 1001 in the first region 2001 proceeds, and the change in transmittance in the first region 2001 is not substantially visible. In this case, it is preferable that T consists of a time T _Fwd for applying V _Fwd and a time T _Rev for applying V _Fwd . Furthermore, the drive circuit 1010 can preferably control the transmittance gradation by changing the ratio of T _Fwd to T _Rev. More specifically, when the drive circuit 1010 controls the variable transmittance gradation of the EC element 1009, it can preferably control the transmittance gradation by changing the ratio of T _Fwd to T _Rev in one cycle of pulse width modulation drive.

The drive circuit 1010 according to this embodiment may be used by switching between the aforementioned repeated voltage application drive method and typical EC element drive methods such as DC or pulse-width modulated voltage application of drive voltage/open-circuit voltage, depending on the situation and conditions. Specifically, the drive method can be switched as follows: That is, when using an apodization filter or aperture, if you want to reduce the light intensity not only in the periphery but also in the center for reasons such as slow shutter speed photography or video recording, select the DC or pulse-width modulated voltage application drive method. On the other hand, when using an apodization filter or aperture, if you want to increase the light intensity for blur prevention or fast shutter speed photography, select the repeated voltage application drive method described above.

It is known that the current required to achieve the same dimming state in an EC element decreases as the temperature decreases. This decrease in current leads to a slowing of the effective voltage gradation and the transmittance gradation. To address this, a temperature sensor is preferably provided in the EC device 1000 according to this embodiment. In this case, it is preferable to apply the aforementioned preset voltage-time ratio to the temperature measured by the temperature sensor. Specifically, for example, when the temperature decreases, an electrochemical reaction that increases the transmittance of the EC layer 1002 is promoted to compensate for the current decrease due to the temperature drop.

As described above, the EC device 1000 according to this embodiment repeatedly supplies a voltage that promotes an electrochemical reaction that reduces the transmittance of the EC layer 1002 and a voltage that promotes an electrochemical reaction that increases the transmittance of the EC layer 1002, via the drive circuit 1010. As a result, the following effects can be obtained with the EC device 1000 according to this embodiment.

Conventional driving methods using DC or pulse-width modulated voltage application of drive voltage/open-circuit voltage controlled the transmittance gradation by controlling the current based on the effective voltage. This resulted in the problem that both the transmittance gradation and the maximum transmittance changed simultaneously. In contrast, the driving method using the drive circuit 1010 of the EC device 1000 in this embodiment allows for current control through electrochemical reaction control that does not increase transmittance, enabling the voltage drop profile to be changed independently of the transmittance. This allows for highly flexible control of the transmittance gradation in this embodiment. Specifically, when applied to lenses or cameras, it enables the acquisition of high-quality images with suppressed signal degradation. Furthermore, when applied to eyeglasses or windows, it enables the realization of desired gradation patterns, improving the functionality of the product.

Furthermore, as a prior example, a method has been reported in which a voltage of opposite polarity to that used during coloring is applied to the EC layer to improve the rate of transmittance increase in an EC element having a complementary EC layer (Prior Example 1: Japanese Patent Publication No. 2020-16805). This method accelerates the reaction that converts the dimmed EC compound to a transparent state by applying a voltage of opposite polarity to the electrode. Since this method improves the rate of transmittance increase in the EC element, it is performed in a time domain in which the change in transmittance can be visually observed.

In contrast, the EC device 1000 according to this embodiment, as explained in the section on the drive circuit 1010, primarily aims to control the steady-state gradation pattern of the EC element 1009, and thus differs in purpose from that of the Prior Art 1. Therefore, in this embodiment, a voltage that promotes an electrochemical reaction to decrease the transmittance of the EC layer 1002 and a voltage that promotes an electrochemical reaction to increase the transmittance of the EC layer 1002 are repeatedly applied. In this embodiment, the drive is performed in a time domain where the change in the transmittance of the EC element 1009 is substantially invisible. In this respect, the EC device 1000 according to this embodiment is clearly different from the configuration of the Prior Art 1. Specifically, if the voltage application method of the Prior Art 1 were applied as is, the change in the transmittance gradation would be visible, and it would not contribute to achieving steady-state gradation pattern control of the EC element during drive.

Furthermore, as another prior example, a driving method has been reported for when an EC element is driven using pulse width modulation of the drive voltage/open circuit voltage, and it is necessary to move the EC element from a high light-transmitting state to a very low light-transmitting state (Prior Example 2: Japanese Patent No. 6727755). This method involves short-circuiting the pair of electrodes when no voltage is applied during one cycle of the pulse width modulation drive. This method deals with the case where, when using pulse width modulation drive, the time required to apply the voltage to bring the EC compound into a low light-transmitting state is smaller than the transient response time of the electrochemical reaction. In this case, the calculated value of the time required to apply the voltage to bring the EC compound into a low light-transmitting state is too small and becomes smaller than the transient response time of the electrochemical reaction, making it difficult to control with pulse width modulation. This method achieves a very low light-transmitting state by adding a short-circuit time (time to bring the EC compound into a high light-transmitting state) to the voltage application required to bring the EC compound into a low light-transmitting state, only when such a very low light-transmitting state is to be achieved. Furthermore, in Prior Example 2, it is stated that when achieving a lower light transmission state than the very slight low light transmission state described above, if the time for applying the voltage to bring the EC compound into a low light transmission state is longer than the transient response time of the electrochemical reaction, the electrodes should not be short-circuited but instead an open circuit should be used.

On the other hand, the EC device 1000 according to this embodiment forms a clear transmittance gradient in the transmittance changing section 2010 of the EC element 1009. This transmittance gradient is formed by the effective voltage gradient formed within the electrode 1001 due to the voltage drop caused by the electrode resistance when current flows through the electrode 1001, and by the transmittance of the EC element 1009 changing depending on the effective voltage of the electrode. In this embodiment, since the current that flows when achieving a very slight low light transmittance state, as in the aforementioned Prior Example 2, is minute, the voltage drop caused by the electrode resistance is small, and a transmittance gradient is hardly formed. Furthermore, in order to form a clear low light transmittance state, such as forming a clear transmittance gradient in the transmittance changing section 2010 of the EC element 1009, as in the EC device 1000 according to this embodiment, Prior Example 2 describes not short-circuiting the electrodes but making it an open circuit. In this respect, the EC device 1000 according to this embodiment is clearly different from the configuration of Prior Example 2. Specifically, if the voltage application method of Prior Example 2 is applied as is, a transmittance gradient will not be formed when employing a driving method that short-circuits the pair of electrodes when no voltage is applied. Furthermore, if a driving method that leaves the pair of electrodes open when no voltage is applied (a typical driving method involving pulse-width modulated voltage application of the drive voltage/open-circuit voltage) is employed, the maximum transmittance of the gradient filter will also decrease. These factors do not contribute to reducing the impact on the maximum transmittance when controlling the optical transmission region of the EC element.

The EC device 1000 according to this embodiment can be applied to optical applications such as variable apodization filters, variable apertures, and variable half-ND filters. Furthermore, the EC device 1000 according to this embodiment can be applied to eyeglasses and windows. When applied to eyeglasses and windows, it is possible to achieve desired gradation patterns, improving the functionality of the product. The EC device 1000 according to this embodiment can also be used as an imaging device, lens unit, or a component attached thereto. The imaging device can be applied to products that have a combination of light intensity adjustment and an image sensor. For example, an optical filter using the EC device 1000 according to this embodiment can be applied to cameras, digital cameras, video cameras, and digital video cameras. Furthermore, an optical filter using the EC device 1000 according to this embodiment can also be applied to products with built-in imaging devices, such as mobile phones, smartphones, PCs, and tablets. By using the EC device 1000 according to this embodiment as an optical filter, it becomes possible to partially and freely change the light intensity within the field of view with a single filter, which is effective in reducing the number of components and saving space.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(1) Fabrication of EC elements (a) Fabrication of EC element bodies The EC elements of the EC device (apodization filter device) of the embodiment outlined in Figure 3 were fabricated by the following process. First, silver wiring (15.8 mΩ/□, 2.2 mm wide) was formed on the outer circumference of a glass coated with a uniform ITO film with a sheet resistance of 60 Ω/□ by mask sputtering, so that the electrode size of the transmittance change area would be a circle of 46 mmφ. Next, a UV-curable sealant mixed with 30 μm spacer beads as a partition was applied to the ITO film, and the substrates were stacked so that the ITO film surfaces of the pair of substrates faced each other, and the sealant was cured by irradiating with UV light.

(b) Injection of electrolyte solution An electrolyte solution (EC solution) was prepared by dissolving an EC compound and PMMA (polymethyl methacrylate resin) in propylene carbonate. As the EC compound, several EC compounds (1) to (6) shown below, synthesized with reference to Japanese Patent Publication No. 2020-95253, were used.

Table 1 below shows the concentrations (unit mmolL ^{- 1} ) of the dimmed states of EC compounds (1) to (6) at this time. The PMMA concentration was set to 25 g/L. Here, EC compounds (1) to (3) are anodic EC compounds which are dihydrophenazine derivatives. EC compounds (4) to (6) are cathodic EC compounds which are viologen derivatives. These EC compounds are low molecular weight organic materials, and the EC elements using them are complementary, floating, and self-decolorizing low molecular weight organic EC elements.

Next, the electrolyte solution prepared in this manner was injected into the void that would become the EC layer through an injection port (not shown) formed in the partition wall, and then sealed with a UV-curable sealant. Thus, an EC element was formed. The formed EC element was a self-decolorizing type EC element in which an anode EC compound and a cathode EC compound were dissolved in the electrolyte solution. Furthermore, this EC element was a normally transparent EC element, exhibiting a transparent state when no voltage was applied from the drive circuit, and a dimmed state when the effective voltage was applied. The first light-transmitting state, closer to the wiring, had lower light transmittance than the second light-transmitting state.

(2) Driving the EC element (a) Advantages over conventional DC driving The EC device was constructed using a potentiostat connected to a function generator as the driving circuit. Transmittance simulations of the EC elements of the example and comparative example were performed using parameters extracted from an EC element with a unit area of 1 cm × 1 cm. In the transmittance simulation, the sheet resistance of the electrode was set to 60 Ω/□ (overall region), the sheet resistance of the wiring to 15.8 mΩ/□, the width of the wiring to 2.2 mm, and the distance between opposing electrodes to 30 μm.

In Example 1, the driving method involved repeatedly applying a +1.4V square wave, which is the voltage that drives the electrochemical reaction that reduces the transmittance of the EC layer, and a -1.4V square wave, which drives the electrochemical reaction that increases the transmittance of the EC layer, which had become a low-light-transmitting state at +1.4V. The driving frequency at this time was selected to be 100 Hz, which is the frequency at which the electrochemical reaction of the EC layer at the electrode proceeds and the change in transmittance in the first region, which is a low-transmittance region close to the wiring, is not substantially visible. The gradation was controlled by the ratio of the time at which +1.4V was applied to the total application time (duty cycle). As explained using Figure 5, in Example 1, the gradation was controlled with V _Fwd = +1.4V, V _Rev = -1.4V, T = 0.01s (= 100 Hz), and duty cycle: T _Fwd / T. On the other hand, DC driving was selected as the driving method for Comparative Example 1. In Comparative Example 1, the gradation was controlled by changing this applied DC voltage.

Figure 6 shows five examples of distance-transmittance profiles from the center of the apodization filter, and two examples of corresponding transmission images, for each of Example 1 and Comparative Example 1. In the graphs shown in Figure 6, the vertical axis represents light transmittance, and the horizontal axis represents the distance from the center of the apodization filter (d = 0.0 is the center, d = 1.0 is the edge).

Figure 6(a) shows the profiles of the apodization filter apparatus of Example 1 when the duty cycle is changed from 0.55 to 0.75 in 0.05 increments. From the results shown in Figure 6(a), it was confirmed that the apodization filter apparatus of Example 1 was able to change the low-transmittance region (control the gradation) without significantly reducing the transmittance in the central part. Furthermore, in the first region, which is the low-transmittance region, the steady-state transmittance change was almost zero and not visible.

In contrast, Figure 6(b) shows the profiles of the apodization filter device of Comparative Example 1 when the DC voltage was varied from 0.5V to 0.9V in 0.1V increments. From the results shown in Figure 6(b), it was confirmed that in the apodization filter device of Comparative Example 1, increasing the applied voltage and expanding the low transmittance region (controlling the gradation) significantly reduced the transmittance in the center of the filter.

From the comparison between Example 1 and Comparative Example 1 described above, the following could be confirmed.
- By repeatedly supplying voltages that promote electrochemical reactions that decrease the transmittance of the EC layer and voltages that promote electrochemical reactions that increase the transmittance of the EC layer, the influence on the maximum transmittance when controlling the light transmission region of the EC element can be reduced.

- By repeatedly supplying voltage in a time domain where the electrochemical reaction of the EC layer in the electrode in the first region proceeds and the change in transmittance in the first region is substantially invisible, the influence on the maximum transmittance when controlling the light transmission region of the EC element can be reduced.

- By setting the voltage that drives the electrochemical reaction that increases the transmittance of the EC layer to a voltage with the opposite polarity to the voltage that drives the electrochemical reaction that decreases the transmittance of the EC layer, the influence on the maximum transmittance when controlling the light transmission region of the EC element can be reduced.

- By using an appropriate drive circuit for an EC device where the first light transmission state (closer to the wiring) has lower light transmittance than the second light transmission state (further from the wiring), it is possible to provide an apodization filter that reduces the influence on the maximum transmittance during light transmission region control of the EC element.

- By using a drive circuit that changes the ratio of the time supplied between the voltage that drives the electrochemical reaction that increases the transmittance of the EC layer and the voltage that drives the electrochemical reaction that decreases the transmittance of the EC layer, the influence on the maximum transmittance when controlling the light transmission region of the EC element can be reduced.

- A drive circuit may be used that changes the ratio of the time supplied between the voltage that promotes an electrochemical reaction increasing the transmittance of the EC layer and the voltage that promotes an electrochemical reaction decreasing the transmittance of the EC layer during one cycle of pulse width modulation drive. This reduces the influence on the maximum transmittance when controlling the light transmission region of the EC element.

(b) Advantages of applying reverse polarity voltage As a driving method for Examples 2 and 3, we will describe the case in which a voltage of +0.9V is applied, which is a voltage that promotes an electrochemical reaction that reduces the transmittance of the EC layer, and a different voltage is applied that promotes an electrochemical reaction that increases the transmittance of the EC layer, which has become a low light transmittance state at +0.9V.

In Example 2, a voltage of -0.9V was applied as the driving method to advance the electrochemical reaction that increases the transmittance of the EC layer, which was in a low light transmittance state at +0.9V. In Example 3, a voltage of 0V was applied as the driving method to advance the electrochemical reaction that increases the transmittance of the EC layer, which was in a low light transmittance state at +0.9V. As explained using Figure 5, in the driving method of Example 2, V _Fwd = +0.9V, V _Rev = -0.9V, T = 0.01s (= 100Hz), and duty cycle: T _Fwd / T = 0.65 were selected. In the driving method of Example 3, the same conditions as in Example 2 were used, except that V _Rev was changed to 0V. Here, in Example 2, a voltage with the opposite polarity to the voltage that advances the electrochemical reaction that advances the transmittance of the EC layer was applied as the voltage that advances the electrochemical reaction that advances the transmittance of the EC layer. On the other hand, in Example 3, a voltage of 0V, which is not the opposite polarity of the voltage that drives the electrochemical reaction, was applied as the voltage that drives the electrochemical reaction that drives the electrochemical reaction that drives the electrochemical reaction that drives the electrochemical reaction that drives the electrochemical reaction, which is the opposite polarity of the voltage that drives the electrochemical reaction that drives the electrochemical reaction that drives the electrochemical reaction, which is the opposite polarity of

Figure 7 shows the distance-transmittance profiles from the center of the apodization filter for each of Examples 2 and 3. In Example 2, where a reverse polarity -0.9V voltage was applied, it was confirmed that the low-transmittance region could be changed without a significant decrease in transmittance in the central area. In contrast, in Example 3, where a non-reverse polarity 0V voltage was applied, a slight decrease in transmittance in the central area was observed.

The results shown in Figure 7 confirm the effectiveness of applying a voltage with the opposite polarity to the voltage that promotes the electrochemical reaction that decreases the transmittance of the EC layer, as the voltage that promotes the electrochemical reaction that increases the transmittance of the EC layer. In other words, it was confirmed that applying such a voltage with the opposite polarity can more effectively reduce the influence on the maximum transmittance when controlling the light transmission region of the gradient EC element.

[Second Embodiment]
A lens unit according to a second embodiment of the present invention will now be described. The lens unit according to this embodiment may consist of an imaging optical system having a plurality of lenses and an optical filter. As the optical filter, the EC element of the EC device according to the first embodiment can be used. The optical filter may include a drive circuit for driving the EC element. The optical filter may be provided either between the plurality of lenses of the imaging optical system or on the outside of the lenses. It is preferable that the optical filter be placed on the optical axis of the lens.

By configuring a lens unit having an optical filter using an EC element of the EC device according to the first embodiment, the light incident on the lens unit can be modulated according to various transmittance profiles.

[Third Embodiment]
An imaging device according to a third embodiment of the present invention will be described with reference to Figure 8. Figure 8 is a schematic diagram showing an example of the configuration of the imaging device according to this embodiment.

The imaging device according to this embodiment may be configured to include an optical filter and a light-receiving element that receives light that has passed through the optical filter. Specific examples of imaging devices include cameras, video cameras, and camera-equipped mobile phones. The imaging device may also be configured such that the main body having the light-receiving element and the lens unit having the lens are separable. In the case where the imaging device is separable from the main body and the lens unit, the present invention also includes configurations where a separate optical filter is used during imaging. In such cases, possible placement locations for the optical filter include the outside of the lens unit, between the lens unit and the light-receiving element, and between multiple lenses (when the lens unit has multiple lenses).

Figure 8(a) is a schematic diagram of an example of an imaging device in which an optical filter is arranged on the lens unit. Figure 8(b) is a schematic diagram of an example of an imaging device in which an optical filter is arranged on the imaging device.

The imaging device 200 includes a lens unit 202 and an imaging unit 203. The lens unit 202 includes an optical filter 201 and an imaging optical system having multiple lenses or lens groups. The optical filter 201 is the optical filter of the second embodiment described above.

Figure 8(a) shows a rear-focusing zoom lens, represented as lens unit 202, where focusing occurs behind the aperture. Lens unit 202 has four lens groups, arranged in order from the subject side: a first lens group 204 with positive refractive power, a second lens group 205 with negative refractive power, a third lens group 206 with positive refractive power, and a fourth lens group 207 with positive refractive power. Magnification is achieved by changing the distance between the second lens group 205 and the third lens group 206, and focusing is performed by moving a portion of the lens group 207.

The lens unit 202 has, for example, an aperture diaphragm 208 between the second lens group 205 and the third lens group 206, and an optical filter 201 between the third lens group 206 and the fourth lens group 207. The light passing through the lens unit 202 is arranged to pass through the first to fourth lens groups 204 to 207, the aperture diaphragm 208, and the optical filter 201, allowing for adjustment of the light intensity using the aperture diaphragm 208 and the optical filter 201.

The lens unit 202 is detachably connected to the imaging unit 203 via a mounting member (not shown).

In this embodiment, the optical filter 201 is positioned between the third lens group 206 and the fourth lens group 207 within the lens unit 202. However, the imaging device 200 is not limited to this configuration. For example, the optical filter 201 may be located either before (on the subject side) or after (on the imaging unit 203 side) the aperture diaphragm 208, or before, after, or between any of the first to fourth lens groups 204 to 207. Furthermore, positioning the optical filter 201 at a point where light converges offers advantages such as reducing the area of the optical filter 201.

Furthermore, the configuration of the lens unit 202 is not limited to the above configuration and can be selected as appropriate. For example, in addition to a rear-focusing type, it may also be an inner-focusing type that focuses in front of the aperture, or any other type. In addition to zoom lenses, special lenses such as fisheye lenses and macro lenses can also be selected as appropriate.

The imaging unit 203 comprises a glass block 209 and a light-receiving element 210. The glass block 209 is a glass block such as a low-pass filter, faceplate, or color filter. The light-receiving element 210 is a sensor that receives light that has passed through the lens unit, and can be an image sensor such as a CCD or CMOS. Alternatively, it may be an optical sensor such as a photodiode, which acquires and outputs information on light intensity or wavelength.

As shown in Figure 8(a), when the optical filter 201 is incorporated into the lens unit 202, the drive unit may be located inside the lens unit 202 or outside of it. If located outside the lens unit 202, the drive unit is connected to the EC element inside the lens unit 202 via wiring for drive control.

Furthermore, in the configuration of the imaging device 200 described above, the optical filter 201 is located inside the lens unit 202. However, the present invention is not limited to this configuration; the optical filter 201 can be located at an appropriate location inside the imaging device 200, and the light-receiving element 210 can be positioned to receive light that has passed through the optical filter 201.

For example, as shown in Figure 8(b), the imaging unit 203 may have an optical filter 201. Figure 8(b) is a diagram illustrating the configuration of another example of the imaging device of this embodiment, and is a schematic diagram of the configuration of an imaging device having an optical filter 201 in the imaging unit 203. In Figure 8(b), for example, the optical filter 201 is positioned directly in front of the light-receiving element 210. If the imaging device itself has a built-in optical filter 201, the connected lens unit 202 itself does not need to have an optical filter 201, making it possible to configure a dimmable imaging device using an existing lens unit 202.

The imaging device 200 of this embodiment is applicable to products that have a combination of light intensity adjustment and a light-receiving element. For example, it can be used in cameras, digital cameras, video cameras, and digital video cameras, and is also applicable to products that incorporate an imaging device, such as mobile phones, smartphones, PCs, and tablets.

According to the imaging device 200 of this embodiment, by using the optical filter 201 as a light-adjusting element, it becomes possible to appropriately vary the light-adjusting amount with a single filter, offering advantages such as a reduction in the number of elements and space savings.

[Fourth Embodiment]
A window material according to a fourth embodiment of the present invention will be described with reference to Figure 9.
The window material according to this embodiment has an electrochromic device 1000 according to the first embodiment, and includes an EC element 1009 and a drive circuit 1010.

The drive circuit 1010 drives the EC element 1009 and constitutes a drive circuit that adjusts the amount of light passing through the EC element 1009. The drive circuit 1010 can be composed of active elements. Examples of active elements include transistors. The transistor may have an oxide semiconductor such as InGaN (InGaZnO) in its active region. The window material according to this embodiment can also be called a variable transmittance window.

Figure 9(a) is an overview diagram showing a dimmable window as a window material using an EC element, and Figure 9(b) is a schematic diagram showing a cross-sectional view of Figure 9(a) along the line X-X'. The dimmable window 300 of this embodiment consists of an EC element 1009 (optical filter), a transparent plate 313 which is a substrate that sandwiches it, and a frame 312 that surrounds and integrates the entire structure. The drive circuit 1010 may be integrated within the frame 312, or it may be located outside the frame 312 and connected to the EC element 1009 through wiring.

The transparent plate 313 is not particularly limited as long as it is made of a material with high light transmittance, but glass is preferable considering its use as a window. The material of the frame 312 is not specified, but any frame that covers at least a portion of the EC element 1009 and has an integrated form may be considered as such. In Figure 9, the EC element 1009 is a component independent of the transparent plate 313, but for example, the base material 1006 of the EC element 1009 may be considered as the transparent plate 313.

The dimmable window 300 can be used, for example, to adjust the amount of sunlight entering a room during the day. Because it can be used to adjust not only the amount of sunlight but also the amount of heat, it can be used to control the brightness and temperature of a room. Furthermore, it can be used as a shutter to block the view from outside into the room. Such dimmable windows can be applied not only to glass windows in buildings but also to windows in vehicles such as cars, trains, airplanes, and ships.

[Modified Embodiment]
The present invention is not limited to the embodiments described above and can be modified in various ways.
For example, an example in which a part of the configuration of one embodiment is added to another embodiment, or in which a part of the configuration of another embodiment is replaced, is also an embodiment of the present invention.

Furthermore, while the above embodiments show examples of applying the EC element according to the present invention to an optical filter, lens unit, imaging device, and window material, the applications of the EC element according to the present invention are not limited to these.

For example, an EC mirror can be created by providing a reflective material in one of the light paths of an EC element. An EC mirror may be installed in an automobile as an anti-glare mirror. An EC mirror can be constructed by having an EC element and a reflective material inside or outside the EC element. Having a reflective material inside indicates that the electrodes of the EC element are reflective. Having a reflective material outside indicates that the reflective material is provided either in contact with the transparent electrodes of the EC element or via another transparent material.

Furthermore, the above embodiments are merely examples of concrete implementations of the present invention, and the technical scope of the present invention should not be interpreted as being limited by them. In other words, the present invention can be implemented in various forms without departing from its technical concept or its main features.

1000: EC device 1001: electrode 1002: EC layer 1004: wiring 1005: partition wall 1006: substrate 1009: EC element 1010: drive circuit 2001: first region 2002: second region 2010: transmittance change section

Claims (17)

An electrochromic element having a pair of rectangular electrodes, an electrochromic layer disposed between the pair of electrodes, and wiring connected to the pair of electrodes and arranged only on one side of the rectangular electrodes ,
A drive circuit connected to the electrochromic element and supplying voltage to the pair of electrodes via the wiring,
It has,
The electrochromic element is an electrochromic element that forms a transmittance gradient in the transmittance-changing region where the electrochromic layer is arranged, due to the resistance of the electrodes.
The transmittance changing section has a first region that forms a first light transmission state at a position within the electrode of the transmittance changing section that is close to the wiring, and a second region that forms a second light transmission state at a position within the electrode that is further from the wiring than the first region.
The electrochromic apparatus is characterized in that, when controlling the transmittance gradation, the drive circuit repeatedly supplies a first voltage that promotes an electrochemical reaction that reduces the transmittance of the electrochromic layer and a second voltage that promotes an electrochemical reaction that increases the transmittance of the electrochromic layer, at a frequency in the first region where the electrochemical reaction of the electrochromic layer at the electrode proceeds and the change in transmittance in the first region is not visible. The electrochromic apparatus according to claim 1, characterized in that the second voltage is a voltage with the opposite polarity to the voltage that drives an electrochemical reaction that reduces the transmittance of the electrochromic layer. The electrochromic apparatus according to claim 1 or 2, characterized in that the first light transmission state has a lower light transmittance than the second light transmission state. The electrochromic apparatus according to any one of claims 1 to 3, characterized in that, when forming the gradient of transmittance, there is a difference of more than twice between the highest and lowest values of the light transmittance between the first light transmission state and the second light transmission state. The electrochromic apparatus according to any one of claims 1 to 4, characterized in that the drive circuit controls the gradient of transmittance by changing the ratio of the time for supplying the first voltage and the second voltage. The electrochromic apparatus according to any one of claims 1 to 5, characterized in that the frequency at which the drive circuit repeatedly supplies the first voltage and the second voltage is 24 Hz or higher. The electrochromic apparatus according to claim 6, characterized in that the frequency is 60 Hz or higher. The electrochromic apparatus according to claim 7, characterized in that the frequency is 60 Hz or more and 300 Hz or less. The electrochromic apparatus according to any one of claims 1 to 8, characterized in that the drive circuit supplies the first voltage and the second voltage in one cycle of pulse width modulation drive when controlling the transmittance gradation. The electrochromic device according to any one of claims 1 to 9, characterized in that the electrochromic element is a complementary electrochromic element in which the electrochromic layer has at least one of an anode electrochromic compound and a cathode electrochromic compound. The electrochromic apparatus according to claim 10, characterized in that the electrochromic element is a self-decolorizing electrochromic element having a floating electrochromic layer . The electrochromic apparatus according to claim 10 or 11, characterized in that the anodic electrochromic compound is a dihydrophenazine derivative. The electrochromic apparatus according to any one of claims 10 to 12, characterized in that the cathodic electrochromic compound is a derivative of a pyridine salt. An electrochromic apparatus according to any one of claims 1 to 13,
An imaging optical system having multiple lenses,
A lens unit characterized by having the following features. An electrochromic apparatus according to any one of claims 1 to 13,
An imaging device characterized by having an image sensor that receives light transmitted through the electrochromic element of the electrochromic device. An electrochromic apparatus according to any one of claims 1 to 13,
A window material characterized by having a substrate that sandwiches the electrochromic element of the electrochromic apparatus. A method for driving an electrochromic element having a pair of rectangular electrodes, an electrochromic layer disposed between the pair of electrodes , and wiring connected to the pair of electrodes and arranged only on one side of the rectangular electrodes ,
The electrochromic element is an electrochromic element that forms a transmittance gradient in the transmittance-changing region where the electrochromic layer is arranged, due to the resistance of the electrodes.
The transmittance changing section has a first region that forms a first light transmission state at a position within the electrode of the transmittance changing section that is close to the wiring, and a second region that forms a second light transmission state at a position within the electrode that is further from the wiring than the first region.
A method for driving an electrochromic element, characterized in that, when supplying voltage to the pair of electrodes via the wiring and controlling the transmittance gradation, a first voltage that promotes an electrochemical reaction that reduces the transmittance of the electrochromic layer and a second voltage that promotes an electrochemical reaction that increases the transmittance of the electrochromic layer are repeatedly supplied at a frequency in the first region where the electrochemical reaction of the electrochromic layer at the electrodes proceeds and the change in transmittance in the first region is not visible.